1. Field of the Invention
The present invention relates to a gas generator for an air bag for protecting a passenger from an impact of a collision.
2. Description of Related Art
From the point of view of passenger protection, various demands have been made in relation to a gas generator for an air bag which is incorporated into an air bag system installed in an automobile. Examples of these demands include ensuring that the gas generator can be operated reliably over a typical expected lifespan (ten years or more) of the vehicle in which the air bag system is installed.
To reduce the size of the gas generator, it is desirable that a gas generating agent having a lower combustion temperature be used so that a coolant filter can be simplified. Another desirable effect of using a gas generating agent having a lower combustion temperature is that the amount of gas components, such as NOx, generated during combustion of the gas generating agent can be reduced.
However, it is also known that gas generating agents having a low combustion temperature typically suffer from poor ignitability. Nevertheless, to ensure that the gas generator operates reliably, it is desirable that the gas generating agent possesses both good ignitability and good combustibility.
Therefore, improving the cleanness of the gas and reducing the weight of the gas generator are antithetical technologically to ensuring operational reliability in terms of the ignitability and combustibility of the gas generating agent.
Moreover, the output of the gas generator is modified according to the type of vehicle to which the gas generator is installed. However, modifying the container or components inside the container every time the gas generator is installed leads not only to cost increases, but also to errors in the component assembly.
In the gas generator disclosed in JP-A No. 11-334517, a transfer charge is ignited and burned by an activation of an igniter, and a gas generating agent is ignited and burned by the resulting flame. In the gas generator disclosed in WO-A 01/72560, a transfer charge is ignited by the ignition, through electrification of an igniter, and a gas generating agent is burned by the resulting flame. Since the ignitability of a gas generating agent comprising a nitrogen-containing organic compound is particularly poor, an ignition chamber is provided to restrict the outflow of gas in a circumferential direction.
JP-A No. 11-334517 makes no statement as to the combustion temperature of the gas generating agent, and no references are made to problems caused by the combustion temperature. With the constitution disclosed in WO-A 01/72560, a gas generating agent having a lower combustion temperature cannot be burned effectively. Moreover, since there is no statement about using two or more types of gas generating agent having different combustion temperatures, output cannot be adjusted by combining gas generating agents having different combustion temperatures.